axle problems on 3x20 series

It seems there are some axle problems you hear about on some of the 3x20 and 4x20 series tractors. I bought my 3520 in 2010. On the day it arrived I ran it around getting a feel for it, about an hour. I noticed the next day a puddle of fluid on the floor under the axle near the tire. I checked the fluid and the stick was dry.

I called the dealer and tore into them right good. It was a Saturday so I left a voice mail for the salesman and sales manager. They called me first thing Monday morning and had a tech come out and put more fluid in the axle. It didn't take much. I made him leave me the gallon of fluid. The tech said even tho the stick was dry it still had plenty of fluid as to not cause any damage.

60 hrs. later I haven't had a problem since that one time. I always check my fluids before I start it, keeping a close eye on the axle.

Is there a good reason why I had that leak?

Is there anything I should do or any questions to ask before my warranty runs out at the end of the year as far as the axle goes?

Thanks